Manufacturers of asphalt shingles have, for many years, endeavored to produce shingles that resemble natural materials in appearance. Typical materials that manufacturers have sought to have asphalt shingles resemble are natural slate and cedar shakes. Techniques that manufacturers have employed have included applying an overlay to the shingle, or making a multiple-layered or laminated shingle.
In U.S. Pat. No. 4,352,837 to Kopenhaver, an overlay is taught, whereby, after a single layer of shingle is made, comprised of a mat, asphalt, and granules on an upper surface, the single layer thus made receives an overlay in the form of an additional partial coating of asphalt, which in turn, receives additional granules thereon, creating localized areas of additional thickness on the shingle, with such areas of additional thickness having the desired ornamentation.
In U.S. Pat. No. 5,181,361, to Hannah, et al, there is taught a laminated shingle, in which the shingle is comprised of a base layer and a secondary layer, and with a partial top layer, with each of the layers being comprised of an asphaltic web with granules applied to the top of the web, to yield a shingle with some portions being of two-layer thickness and other portions being of three-layer thickness.
Whether the shingle is of the overlay type or of the laminated type, various ornamental effects can be achieved by the use of variously colored granules.
Whether the thicker-appearing shingles are made by overlay techniques or by laminating layers together, there is, in each case, an additional expense associated with doing so, both in the use of additional materials, and in additional manufacturing steps.